Plastic container having a ring-shaped reinforcement and method of making same

ABSTRACT

A plastic container comprises an upper portion including a finish adapted to receive a closure, a lower portion including a base, a sidewall extending between the upper portion and the lower portion, the sidewall having an interior surface and an exterior surface, and a substantially planar reinforcing ring extending substantially perpendicularly from the interior surface of the sidewall. A method of making a plastic container is also disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to plastic containers andmethods of making plastic containers. More particularly, the presentinvention relates to plastic containers having a ring-shapedreinforcement and methods of making plastic containers having aring-shaped reinforcement.

2. Related Art

Plastic containers for storing contents such beverages, sauces,puddings, lotions, soaps, lubricants, and other objects are well knownin the art. It is desirable for these plastic containers to have highhoop strength (i.e., the container's ability to resist ovalizationand/or racking). In order to facilitate stacking and transportation, itis also desirable for plastic containers to have high top load capacity.

In order to increase the hoop strength of plastic containers, it iscommon for the container to have a recessed “waist” that extends aroundthe circumference of the container, for example, near the verticalmidpoint of the container, or just below the dome. However, containershaving a conventional waist often exhibit greatly reduced top loadcapacity. In addition, the conventional waist often detracts from thevisual appeal of the container, and/or limits the amount of designs thatare possible for the container.

Therefore, there remains a need in the art for a plastic containerhaving a reinforcement that provides increased hoop strength whilemaintaining top load capacity. There also remains a need in the art forsuch a plastic container that is visually appealing and provides a highdegree of design flexibility.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a plastic container comprising anupper portion including a finish adapted to receive a closure, a lowerportion including a base, a sidewall extending between the upper portionand the lower portion, the sidewall having an interior surface and anexterior surface, and a substantially planar reinforcing ring extendingsubstantially perpendicularly from the interior surface of the sidewall.

According to one aspect of the invention, the sidewall includes aninterior surface and an exterior surface, and the reinforcing ringextends from the interior surface. Additionally or alternatively, theexterior surface of the sidewall immediately opposite the reinforcingring is substantially free of indentations. Additionally oralternatively, the exterior surface of the sidewall immediately oppositethe reinforcing ring includes a seam.

According to another aspect of the invention, the reinforcing ringcomprises a crease in the sidewall.

According to yet another aspect of the invention, the reinforcing ringcomprises a first portion of the sidewall and a second portion of thesidewall that are folded over one another.

The reinforcing ring defines a nominal height and a nominal width, andthe nominal width can be at least about three times the nominal height.

The present invention is also directed to a method of blow molding aplastic container, comprising inserting a preform into a mold, thepreform comprising an upper portion, a lower portion, and a sidewallextending between the upper portion and the lower portion, stretchingthe preform with a stretch rod, contacting the stretch rod with aportion of the sidewall to form a ring of material around the stretchrod, and inflating the preform into a container. The ring of materialforms a reinforcing ring on the container.

According to one aspect of the invention, the step of stretching thepreform with the stretch rod causes the portion of the sidewall tocontract around the stretch rod to form the ring of material.Additionally or alternatively, the method can further include the stepof selectively forming a reduced-temperature region on the sidewall thatsubstantially coincides with the portion of the sidewall that contractsaround the stretch rod.

According to another aspect of the invention, the method can furtherinclude the step of preheating the preform to a first temperature.Additionally or alternatively, the method can include the step ofcooling a portion of the sidewall to a second temperature less than thefirst temperature.

According to yet another aspect of the invention, the ring of materialdefines an upper section of the sidewall and a lower section of thesidewall, and during the step of inflating the preform into thecontainer, a portion of the upper section and a portion of the lowersection fold over one another.

Further objectives and advantages, as well as the structure and functionof preferred embodiments will become apparent from a consideration ofthe description, drawings, and examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of a preferredembodiment of the invention, as illustrated in the accompanying drawingswherein like reference numbers generally indicate identical,functionally similar, and/or structurally similar elements.

FIG. 1 is a perspective view of an exemplary embodiment of a plasticcontainer according to the present invention;

FIG. 2 is a side view of the plastic container of FIG. 1;

FIG. 3 is a partial, cross-sectional view of an exemplary sidewall ofthe plastic container of FIG. 1; and

FIG. 4 is a side view of one step in an exemplary embodiment of a methodof blow molding a plastic container according to the present invention,with the mold shown in cross-section; and

FIGS. 5-7 depict additional steps of the method of blow molding aplastic container, with the mold and a preform shown in cross-section.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention are discussed in detail below. Indescribing embodiments, specific terminology is employed for the sake ofclarity. However, the invention is not intended to be limited to thespecific terminology so selected. While specific exemplary embodimentsare discussed, it should be understood that this is done forillustration purposes only. A person skilled in the relevant art willrecognize that other components and configurations can be used withoutdeparting from the spirit and scope of the invention. All referencescited herein are incorporated by reference as if each had beenindividually incorporated.

Referring to FIGS. 1 and 2, an exemplary embodiment of a container 10according to the present invention is shown. Container 10 can be used topackage a wide variety of liquid, viscous, or solid products including,for example, juices or other beverages, yogurt, sauces, pudding,lotions, soaps in liquid or gel form, and bead shaped objects such ascandy.

Container 10 generally includes an upper portion 12, a lower portion 14,and a sidewall 16 extending between upper portion 12 and lower portion14. Upper portion 12 can include a finish 18 having one or more threads20, or other features, configured to secure a closure, such as a cap(not shown) to container 10. Lower portion 14 can include a base 22adapted to support container 10 in an upright position on asubstantially flat surface, such as a table. Although not shown in thefigures, base 22 can include any number of known features that reinforcethe base 22, compensate for internal pressure or vacuum within container10, or provide other desired functions.

As shown in FIGS. 1 and 2, sidewall 16 is substantially tubular and hasa generally circular transverse cross-section. However, one of ordinaryskill in the art will appreciate that any cross-sectional geometry ispossible. Other possible cross-sectional geometries include, forexample, an oval transverse cross-section, a substantially squaretransverse cross-section, other substantially polygonal transversecross-sectional geometries such as triangular or pentagonal, andcombinations of curved and arced shapes with linear shapes. Irregularcross-sectional geometries are also possible. As will be understood,when container 10 has a substantially polygonal transversecross-sectional geometry, the corners of the polygon are typicallyrounded or chamfered.

Still referring to FIGS. 1 and 2, container 10 includes a reinforcingring 24 that extends from sidewall 16 around the circumference ofcontainer 10. As shown in the figures, reinforcing ring 24 may besubstantially planar, and/or may be substantially perpendicular tosidewall 16. Reinforcing ring 24 can increase the hoop strength ofsidewall 16 without significantly reducing the top load capacity ofcontainer 10. Reinforcing ring 24 is not limited to the position shownin FIGS. 1 and 2, and may be provided at any position along the heightof container 10. In addition, container 10 may include any number ofreinforcing rings 24 as may be needed to suit a specific application ofcontainer 10.

Referring to FIG. 3, sidewall 16 includes an interior surface 16A and anexterior surface 16B. In the embodiment shown, reinforcing ring 24extends from interior surface 16A. The region of exterior surface 16Blocated immediately opposite reinforcing ring 24, indicated in FIG. 3 asR, is preferably substantially free of indentations. That is, region Rpreferably does not have an indentation corresponding in shape/size toreinforcing ring 24, as is typical of prior art containers. Rather, inthe exemplary embodiment shown, region R includes at most only a minorseam 26, which only has minor effects on the aesthetics of container 10.The lack of any significant indentations in region R provides acontainer that has greater top load capacity when compared toconventional containers in which a reinforcing feature such as a ring orrib projecting from one side of the sidewall typically results in acorresponding indentation on the opposite side of the sidewall. Inaddition, the lack of any significant indentation in region R provides areinforcement that has minimal effect on the aesthetics of container 10,thus providing additional design flexibility.

Still referring to FIG. 3, reinforcing ring 24 may comprise a creasethat is formed in sidewall 16, for example, during the process of makingcontainer 10. In the exemplary embodiment shown, reinforcing ring 24comprises a first portion 24A and a second portion 24B. First portion24A and second portion 24B can be pinched or folded over one another,for example, during blow molding of container 10, as will be describedin more detail below.

As shown in FIG. 3, reinforcing ring 24 may define a nominal height Ythat extends substantially parallel to the longitudinal axis ofcontainer 10, and a nominal width X that is perpendicular to thelongitudinal axis. The nominal height Y and/or the nominal width X canbe adjusted to provide certain characteristics to the container 10, suchas hoop strength. According to one exemplary embodiment, nominal width Xmay be at least about three times the nominal height Y.

Container 10 may be able to withstand the rigors of hot fill processing.In a hot fill process, a product is added to the container at anelevated temperature, about 82° C., which can be near the glasstransition temperature of the plastic material, and the container iscapped. As the container and its contents cool, the contents tend tocontract and this volumetric change creates a partial vacuum within thecontainer. In the absence of some means for accommodating these internalvolumetric and barometric changes, containers tend to deform and/orcollapse. For example, a round container can undergo ovalization, ortend to distort and become out of round. Containers of other shapes canbecome similarly distorted. In addition to these changes that adverselyaffect the appearance of the container, distortion or deformation cancause the container to lean or become unstable. This is particularlytrue where deformation of the base region occurs. Container 10withstands these tendencies by incorporating one or more reinforcingrings 24.

Container 10 can have a one-piece construction and can be prepared froma monolayer plastic material, such as a polyamide, for example, nylon; apolyolefin such as polyethylene, for example, low density polyethylene(LDPE) or high density polyethylene (HDPE), or polypropylene; apolyester, for example polyethylene terephthalate (PET), polyethylenenaphtalate (PEN); or others, which can also include additives to varythe physical or chemical properties of the material. For example, someplastic resins can be modified to improve the oxygen permeability.Alternatively, the container can be prepared from a multilayer plasticmaterial. The layers can be any plastic material, including virgin,recycled and reground material, and can include plastics or othermaterials with additives to improve physical properties of thecontainer. In addition to the above-mentioned materials, other materialsoften used in multilayer plastic containers include, for example,ethylvinyl alcohol (EVOH) and tie layers or binders to hold togethermaterials that are subject to delamination when used in adjacent layers.A coating may be applied over the monolayer or multilayer material, forexample to introduce oxygen barrier properties. In an exemplaryembodiment, the present container is prepared from PET.

With reference to FIGS. 4-7, a method of blow molding a plasticcontainer according to the present invention is shown and described.Prior to or concurrent with the blow molding process, a preform 40 isprepared from a thermoplastic material, for example, by an injectionmolding process. Referring to FIG. 4, one exemplary embodiment ofpreform 40 can include an open upper portion 42, a closed lower portion44, and a sidewall 46 extending between the upper portion 42 and thelower portion 44. The upper portion 42 of preform 40 can include afinish having have one or more threads 48, or other features, formedthereon for securing a closure to the container once completed.Alternatively, the finish and/or threads can be formed during the blowmolding process, as will be known by one of ordinary skill in the art.Preform 40 can generally define a longitudinal axis 49, shown in FIG. 4

Preform 40 is optionally preheated and then inserted into an open moldincluding mold halves 50A and 50B (shown in cross-section), which areclosed about preform 40 and cooperate to provide a cavity 52 into whichpreform 40 is eventually blown to form a finished container. A stretchrod 54, shown in FIGS. 5-7, is then inserted into the open upper portion42 of the preform 40 until it contacts the closed lower portion 44.Continued movement of stretch rod 54 in this direction (direction S inFIG. 5) stretches preform 40 along its longitudinal axis 49. Prior to orconcurrent with this stretching operation, a small amount of air canoptionally be “preblown” into preform 40 under low pressure throughvents 56 in stretch rod 54 to partially inflate preform 40.

As best shown in FIG. 5, stretching of the preform 40 along its axis 49causes sidewall 46 to contract inward toward stretch rod 54. Withsufficient stretching of preform 40 in this manner, sidewall 46 willcontract until a portion of it contacts stretch rod 54, as shown,thereby forming a ring of material 58 extending around stretch rod 54.Due to possible temperature differences between the preform 40 (e.g.,relatively warm) and the stretch rod 54 (e.g., relatively cool), thering of material 58 may adhere to and/or harden around stretch rod 54.

Preform 40 is next inflated under high pressure, for example, by blowingair through vents 56. As shown in FIG. 6, the regions of the sidewall 46above and below the ring of material 58 initially expand outward due tothe air pressure. The ring of material 58, however, remains adhered toand/or hardened around the stretch rod 54, and does not initially expandoutward. The air pressure can cause the ring of material 58 to pinchaway from sidewall 46, and can divide sidewall 46 into an upper section46A and a lower section 46B, which may fold over on one another.Depending on the temperature of the preform 40, the upper section 46Aand the lower section 46B may permanently bond to one another.

Continued application of high air pressure inside preform 40 eventuallycauses the ring of material 58 to expand away from stretch rod 54, andalso causes the preform 40 to fully expand until it conforms to the moldcavity 52, as shown in FIG. 7. At this point, the container is fullyformed, and the ring of material 58 forms a reinforcing ring thatextends from the interior surface of the sidewall of the finishedcontainer. In the exemplary embodiment shown in FIG. 7, the reinforcingring 58 is substantially planar and substantially perpendicular to thesidewall of the finished container.

At this point, the supply of air pressure can be turned off, and thestretch rod 54 can be removed. The mold halves 50A and 50B separate fromone another and release the finished container.

In order to facilitate accurate placement of the reinforcing ring on thesidewall of the finished container, as well as consistent sizing of thereinforcing ring, it may be desirable to selectively form areduced-temperature region on the portion of the preform 40 thatcoincides with the area of the finished sidewall where the reinforcingring is to be located. This reduced-temperature region will have ahigher strength as compared to the surrounding warmer areas, and will bemore prone to contracting around the stretch rod 54 during thestretching process. The size and location of the reduced-temperatureregion can control the position and geometry of the resultingreinforcing ring on the finished container. The reduced-temperatureregion can be formed, for example, by preheating the preform 40 prior toplacement in the mold, and subsequently cooling the desired region.Alternatively, the reduced-temperature region can be formed by heatingthe areas of the preform 40 surrounding the reduced-temperature region,but not the reduced-temperature region itself. One of ordinary skill inthe art will appreciate that any number of other techniques can beimplemented to create the reduced-temperature region.

The embodiments illustrated and discussed in this specification areintended only to teach those skilled in the art the best way known tothe inventors to make and use the invention. Nothing in thisspecification should be considered as limiting the scope of the presentinvention. All examples presented are representative and non-limiting.The above-described embodiments of the invention may be modified orvaried, without departing from the invention, as appreciated by thoseskilled in the art in light of the above teachings. It is therefore tobe understood that, within the scope of the claims and theirequivalents, the invention may be practiced otherwise than asspecifically described.

1. A plastic container comprising: an upper portion including a finishadapted to receive a closure; a lower portion including a base; asidewall extending between the upper portion and the lower portion, thesidewall having an interior surface and an exterior surface; and asubstantially planar reinforcing ring extending substantiallyperpendicularly from the interior surface of the sidewall.
 2. Theplastic container of claim 1, wherein the exterior surface of thesidewall immediately opposite the reinforcing ring is substantially freeof indentations.
 3. The plastic container of claim 2, wherein theexterior surface of the sidewall immediately opposite the reinforcingring includes a seam.
 4. The plastic container of claim 1, wherein thereinforcing ring comprises a crease in the sidewall.
 5. The plasticcontainer of claim 1, wherein the reinforcing ring comprises a firstportion of the sidewall and a second portion of the sidewall that arefolded over one another.
 6. The plastic container of claim 1, whereinthe reinforcing ring defines a nominal height and a nominal width, andthe nominal width is at least about three times the nominal height.
 7. Amethod of blow molding a plastic container, comprising: inserting apreform into a mold, the preform comprising an upper portion, a lowerportion, and a sidewall extending between the upper portion and thelower portion; stretching the preform with a stretch rod; contacting thestretch rod with a portion of the sidewall to form a ring of materialaround the stretch rod; and inflating the preform into a container,wherein the ring of material forms a reinforcing ring on the container.8. The method of claim 7, wherein the step of stretching the preformwith the stretch rod causes the portion of the sidewall to contractaround the stretch rod to form the ring of material.
 9. The method ofclaim 8, further comprising the step of selectively forming areduced-temperature region on the sidewall, wherein thereduced-temperature region substantially coincides with the portion ofthe sidewall that contracts around the stretch rod.
 10. The method ofclaim 7, further comprising the step of preheating the preform to afirst temperature.
 11. The method of claim 10, further comprising thestep of cooling a portion of the sidewall to a second temperature lessthan the first temperature.
 12. The method of claim 7, wherein the ringof material defines an upper section of the sidewall and a lower sectionof the sidewall, and during the step of inflating the preform into thecontainer, a portion of the upper section and a portion of the lowersection fold over one another.
 13. The method of claim 7, wherein thecontainer includes a container sidewall having an interior surface andan exterior surface, and the reinforcing rings extends from the interiorsurface.
 14. The reinforcing ring of claim 13, wherein the reinforcingring is substantially planar and substantially perpendicular to thesidewall.
 15. The method of claim 7, wherein the upper portion definesan opening in the preform, and the lower portion is closed, and the stepof stretching the preform with the stretch rod includes inserting thestretch rod through the opening and contacting the closed lower portion.